Gas lift valves



Aug. 27, 1968 Filed Feb. l, 1 966 J. B. FOX ETAL GAS LIFT VALVES 5 Sheets-Sheet 1 4 .ff .oya/ Fox (26am/@J P am INVENTUM 5 Sheets-Sheet 2 a f N A y r I w.. 0 v l y E f Z x JC f A TTOP/VEVJ Aug 27, 1968 J. B. Fox ETAL GAS LIFT VALVES Filed Feb. l, 1966 Aug. 27, 1968 J. B. Fox ETAL GAS LIFT VALVESv 5 Sheets-Sheet Filed Feb. l, 1966 cf. 1905/0/ Fox Caf/e.; am

INVENTORj R/VE VJ United States Patent O 3,398,760 GAS LIFT VALVES J. Boyd Fox and Charles Paul Lamb, Garland, Tex., as-

signors to Merla Tool Corporation, Garland, Tex., a corporation of Texas Filed Feb. 1, 1966, Ser. No. 524,202 9 Claims. (Cl. 137-155) ABSTRACT F THE DISCLOSURE A gas lift valve with a tubular mandrel, a sleeve slidably mounted in the mandrel yand defining a port and a projection around the exterior of the sleeve below the port, a valve ring slidable between the mandrel and sleeve from a position above a port through the mandrel to a position engaging the sleeve projection to shut olf ilow between the ports, a pressure responsive annular ring mounted in a chamber in the mandrel and connected to move the sleeve, the pressure responsive ring having a bleed passage therethrough which is partially blocked by a rin-g in one position and open in another position of the pressure yresponsive annular Iring and a pilot valve controlling uid pressure `delivered to the chamber. This abstract is neither intended to dene the invention of the application which, of course, is 4measured by the claims, nor is it intended to be limiting as to the -scope of the invention in any way.

The present invention relates to valves and particularly to gas lift valves of the pilot operated type.

In many gas lift installations for the production of oil, the space available in the well bore for tubing is relatively small. This is necessarily so in slim yhole well bores and also in multiple completions in which the separate producing formations of the well are produced through separate tubing strings. The usual `gas lift valve which is secured to the side of the tubing mandrel has the disadvantages of requiring excessive space and of possibly being knocked off its mandrel or otherwise damaged in lowering the tubing string into the well bore. In gas lift production of oil, it is :desired that the lgas lift valve have a large ilow capacity and also be sensitive to the gas lift pressures to open 'and close responsive to small changes in such pressures. Many gas lift valves have been made smaller to accommodate the limited space in slim hole and multiple completion well production, but such valves have either sacrificed the sensitivity of the valve or have reduced the ow capacity. In addition to reducing valve sizes in an lattempt to overcome such ditlculties, concentric valves have been installed in mandrels, but these valves have been subject to many disadvantages including loss of sensitivity and also leakage across the valve seals because such valves required the seals to pass across a port in opening and closing. This action will rapidly destroy the seals. It is necessary in the design of gas lift valves, as in the design of all cornmercial equipment, to maintain ka reasonable cost of the equipment.

Therefore, it is an important object of the present invention to provide a gas lift valve which is sufficiently small to be used readily in slim hole wells and multiple completion wells without limiting the capacity of the valve.

ICC

Another object is to provide a gas lift valve including a lfull-size concentric main valve having large ow capacity and long life with a non-concentric side-mounted pilot valve of relatively small size and a high degree of sensitivity.

A further object is to provide an improved pilot-operated concentric gas lift valve having a substantially long service life.

Another object is to provide an improved side mounting of ya valve on a mandrel which reduces the space requirernents to a minimum.

Still a further object is to provide a concentric gas lift valve with a movable ring-shaped seat to function as a back check valve.

A further object is to provide a pilot-operated gas lift valve in a tubing mandrel with a side-mounted pilot valve in which the mandrel coacts with the pilot valve housing to guide the valve member of the pilot valve.

A still further object is to provide a pilot-operated gas lift valve with a piston as a subcombination having a two-stage bleed configuration.

Still another object is to provide a pilot-operated, concentric gas lift valve with an improved power piston assembly having a standard bleed and a high velocity trash dump bleed when the valve is fully opened.

Still a further object is to provide a pilot-operated gas lift valve with a concentric main valve having a large iiow capacity when open and 4which is not subject to the aforementioned disadvantages of rapid seal destruction.

Other objects, features and advantages of the invention will be apparent from the drawings, the specification and the claims.

In the drawings wherein an illustrative embodiment of this invention is s'hown and wherein like Ireference numerals indicate like parts:

FIGURE 1 is a schematic illustration of a section through a well casing in :a producing well to which the gas lift valve of the present invention has been applied.

FIGURES 2A through 2C are partial sectional views of the gas lift v-alve of the present invention; FIGURE 2A being of the upper portion of the device; FIGURE 2B being the intermediate portion of the device; and FIGURE 2C being the lower portion of the device.

FIGURE 3 is a sectional view of the device taken along line 3-3 in FIGURE 2B.

FIGURE 4 is a partial perspective view of the power piston of the present invention.

FIGURE 5 is an elevation view of the lower portion of the Idevice of the present invention in its fully open position.

FIGURE 6 is a schematic line sectional view of the complete gas lift valve of the present invention illustrating the second-stage bleeding or blowdown of the power piston.

FIGURE 7 is a sectional view of the connection of the lower en-d of the pilot valve assembly to the mandrel taken along lines 7-7 in FIGURE 2B.

In the schematic sectional illustration of FIGURE l, the well bore B is shown having the casing C extending down to the producing formation F and the tubing string T extending down through the casing C into the area of the producing formation F. The tubing string T includes two gas lift valves V-l and V-2 of the present invention connected into the tubing string.

As is normal in gas lift production of well liquids,

the lift gas is provided to the casing area surrounding the tubing string and the production of fluids is upwardly through the tubing string. The packer P seals the tubing string to the casing at a position above the producing formation F.

The details of structure are more clearly illustrated in the FIGURE 2 series of views. The gas lift valve of the present invention includes a mandrel 10, a nonconcentric pilot valve assembly 12, a pressure-responsive means indicated generally at 14, responsive to pressure from the pilot valve assembly, and a 'main concentric valve 16 connected to the pressure-responsive means and adapted to close the ports 18 which extend through the lower portion of the mandrel 10.

The mandrel is generally tubular in shape and is provided with the central passageway or bore 20 which extends therethrough for the ow of the production fluids from the formation F. At each end of the mandrel suitable means, such as threads, are provided to secure the mandrel 10 into the tubing string T. The upper portion of the mandrel 10a extends downwardly and connects to the central portion of the mandrel 10b. The upper section 10a of the mandrel 10 extends downwardly beyond its threaded connection with section 10b and is spaced inwardly from section 10b to define the pressure chamber 22. The section 10b of the mandrel extends downwardly and is connected to the coupling section 10c which provides an inner upwardly facing shoulder 24, and the coupling section 10c connects to the lower section 10d of mandrel 10 through which the ports 18 extend. The lowermost section 10e of mandrel 10 connects to section 10d and has an inner shoulder to receive the bumper assembly hereinafter described.

One side of upper section 10a of the mandrel 10 is formed to have a flat surface 11, as best shown in FIG- URE 3, which receives the pilot valve assembly 12. From FIGURES 2A and FIGURE 7 it can be seen that the connection of the pilot valve assembly to the mandrel is accomplished by the engagement of the upper screw 26 and the two lower screws 28 which extend through the pilot valve housing 34 in mandrel section 10a. The surface 11 of the mandrel section 10aa is provided with the semicircular recess 30 which cooperates with the semicircular recess 32 in the housing 34 of the pilot valve assembly 12 to provide a guide for the movement of the pilot valve 36. The housing 34 is provided with apertures 38 extending therethrough as 4best shown in` FIGURES 2B and 3. The lower portion of the housing 34 defines the passage 40 which communicates with the passage 42 in the upper section 10a of the mandrel 10. The upper end of the passage 40 is surrounded by the valve seat 44 on which the valve member 46 seats. Check valve 48 is provided in the passage 40 allowing flow downwardly therethrough, but preventing ow of fluids upwardly through the passage 40. Inasmuch as the pilot valve need pass only a small volume of gas, it may be small in size and fit within the mandrel recess and not extend beyond the nominal diameter of the mandrel as shown in FIGURES 3 and 7.

The pilot valve 36 includes the valve member 46, the stem 50. surrounded by the valve spring 52 and spring stop 54C which is retained by a slot in structural member 34. The bellows 54 is screwed onto stem 50. The upper portion of bellows 54 is retained in the structural member 34 by the bellows stop 54h which is positioned in a slot in structural member 34 and the set screw 54a which is tightened against the top of bellows S4.

As is usual in pilot valves, the bellows section y54 provides a pressure-responsive member for control of the pilot valve. The pilot valve housing 34 is provided with the apertures 38 through which casing pressure passes to expose the exterior of the bellows 54 to such pressure. When the pressure is suticiently high to overcome the force of the valve spring 52, the pilot valve 36 opens to admit gas under pressure from the casing-tubing annulus into the passageway 40. This gas flows through the passage 40, the passage 42 and into the pressure chamber 22. It should be noted that the communication between the passage 40 and the passage 42 is through the radially inwardly extending passage 41 in pilot valve housing 34 and the radially outwardly extending passage 43 in mandrel 10, and sealing means 56 seals between housing 34 and' mandrel section 10a around such communication. The pilot valve assembly 12 is readily installed on the mandrel 10, and, when casing pressure is suiciently high, the pilot valve admits gas under casing pressure to the pressure chamber 22. The pilot valve housing 34 only needs to be sutiiciently strong to properly position the pilot valve 36 independently of theV mandrel 10. When installed, the recess 30 in the mandrel and the recess 32 in the housing 34 guides the movement of the `pilot valve 36. This method of connecting the pilot valve to the mandrel requires much less space than the conventional threaded boss.

The pressure-responsive means 14, as shown, is positioned in the pressure chamber 22. The pressure-responsive means 14 includes the ring shaped power piston 58, the tubular piston rod 60, which connects to the main valve 16, and suitable seals 62 and 64 providing a seal for the piston 58 against the outer and inner surfaces, respectively, of the pressure chamber 22. The spring 66 is positioned below the piston rod 60 in engagement therewith and is supported by the shoulder 24 of the mandrel coupling section 10c. The spring 66 urges the piston rod 60 and the piston 58 upwardly within the pressure chamber 22 and, therefore, urges main valve 16 toward closed position.

In order to provide selectively for casing or tubing pressure on the upper surface of piston S8, a bleed passage 68 is provided extending through the piston 58. The bleed passage 68 provides communication between the pressure chamber 22 above piston 58 to the interior of the mandrel 10 via the passage 70 which extends downwardly through piston rod 60. The upper end of piston rod 60 is provided with the groove 72 in communication with b oth passages 68 and 70. The shallow radial groove 74 extends across the upper surface of piston 58 and intersects with passage 68. The bottom of groove 74 is only slightly below the bottom of the trough on the upper surface of piston 58 to define a restricted .or first-stage bleed passage within the ring 76 when the ring 76 is in its normal position on the bottom surface of the trough of piston 58. When the ring 76 is lifted off the upper surface of piston 58, the second-stage bleed passage is defined solely by the passage 68 through piston 58. The ring 76 has a slot 78 engaging the pin 80 extending outwardly from mandrel section 10a. Responsive to extreme downward movement of piston 58, as hereinafter explained, the pin 80 engages the upper end of slot 78 and lifts one side of ring 76 above the upper surface of piston 58 to allow full flow through passage 68 to clear trash from groove 74. This cleaning of the restricted passage in groove 74 by the second-stage bleeding is necessary as trash, such as small sand particles, may be caught in the restricted passage through groove 74 below ring 76 after first-stage bleed and ultimately interfere with the valve operation.

The main concentric valving means 16 includes the valve sleeve 82 which is connected at its upper end to the lower end of the piston rod 60 whereby the valve sleeve 82 moves responsive to movement of the pressure-responsive means 14. The valve sleeve 82 is provided with a plurality of ports 84 which, in closed position, are located slightly above the ports 18 through the lower mandrel section 10d. When the concentric valving means 16 is open, the ports 18 communicate with the ports 84. To close the concentric valving means the resilient valve seat insert 86, supported ,on the valve sleeve 82 by the collar 88, engages the valve seat on the valve seat ring assembly 92 within the annular space surrounding the valve sleeve 82.

yThe valve seat ring assembly 92 includes the inner ring member 94, the outer ring member 96 and the lower ring member 98. In the valve seating assembly 92, the ring 96, which is plastic, such as polytetrafluoroethylene, is slipped onto the ring 94 and is held in this position by pressing ring 98 onto the ring 94. With the press t between rings 94 and 98, the assembly will act as a unit during operation. The outer ring member 96 is provided with the seal100 to provide a seal `against the interior surface of the lower mandrel section d. The inner ring 94 is provided with a seal 102 to provide a seal between its exterior surface and the interior surface of the outer ring 96. The upper end of the valve seat ring assembly 92 abuts against the lower end of the mandrel coupling 10c in its uppermost position. The lower end of the coupling 10c is slotted at 101 to allow the pressure from within the central bore to be exerted against the upper surface of the members of the valve seat ring assembly 92. In this manner, the valve seat ring assembly 92 acts as a back check valve closing communication between the ports 18 and ports 84 when the tubing pressure exceeds the casing pressure by sliding downwardly to cause engagement between the seat insert 86 and the valve seat 90. A seal 104 is provided surrounding the lower end of the collar 88 and allowing collar 88 to slide back and forth during operation.

As mentioned, the bumper assembly is installed within the lower mandrel section 10e on the shoulder 106. The bumper ring 108 and resilient bumper 110 coact with seat 106 to form the bumper assembly. The bumper ring 108 is positioned within the bore of the mandrel section 10e. The resilient bumper 110 is confined between the flange 112 and the upwardly facing shoulder 106. Thus, when the valve sleeve 82 moves downwardly in response to movement of the pressure-responsive means 14, it engages the top of the bumper ring 108 and the resilient bumper 110 is compressed between the ange 112 and the shoulder 106 providing a rebound impetus to the sleeve valve member 82.

The lower end of the mandrel section 10d is provided with the trash cleaning slots 114 through which any trash collecting in the lower portion of the mandrel above the seal 104 may be discharged. The seal 104 includes the scraper element 116, which is a plastic, such as polytetrauoroethylene, and sealing means, such as the O-rings 118 and 120. Thus, it can be seen as the collar 88 moves downwardly, the upper edge of the scraper element 116 disengages any dirt or trash from the exterior of collar 88 with excess of such dirt or trash being discharged by the ow from the slots 114 through the ports 84.

The main concentric valving means 16, as illustrated in 2C, is closed; resilient seat insert 86 being in engagement with the valve seat 90. FIGURE 5 illustrates the concentric valving means 16 in the open position with the arrows indicating the ow of casing lift gas through the ports 18 and the ports 84 into the bore 20 of the mandrel 10. FIGURE 6 illustrates the extreme position in the downward travel of the piston 58 and the valve sleeve 82 before rebound from the bumper ring 108 whereby the ring 76 has been lifted by pin 80 from engagement with the part of the upper surface of the piston 58 surrounding passage 68 to place the second-stage or large-flow capacity bleeding through the piston 58 in operation.

The operation of the gas lift valve may be seen from the schematic illustrations of FIGURES l and 6. With the valve members of the present invention positioned on the tubing string T, as illustrated in FIGURE 1, the gas lift production of the well fluids from the producing formation F may be commenced by pressuring of the casing C with lift gas. As soon as casing pressure reaches the opening pressure of the pilot valve 36, the valve member 46 lifts off the valve seat 44, and gas under casing pressure is conducted through the apertures 38, the valve seat 44 past the check valve 48 through the passages 40 and 42 into the pressure chamber 22. Once pilot valve 36 is cracked open, the pressure on the under side ofv valve member 46 increases to cause it to move to full open position. With the ring 76 positioned as shown in FIGURE 2B, the increase in gas pressure within the pressure chamber 22 will be exerted against the top of the piston 58. Only a small portion of such gas will be bled through the groove 74 below the ring 76 into the passage 68. The passage 68, the ring 76 and groove 74 are designed to providea greater restriction to the ow than the restriction through the pilot valve 36. Thus, casing pressure will be maintained in pressure chamber 22 as long as pilot valve 36 is open. The downward movement of the piston 58 will, by connection of the piston 60 to the valve sleeve 82, compress the spring 66 and move the valve sleeve 82 downwardly to disengage the resilient seal 86 from the valve seat 90 to provide communication between the ports 18 and 84, which action is the opening of the main concentric valving means 16. Once the resilient seal 86 has moved from the valve seat 90, the casing pressure will be exerted downwardly on a small annular area defined by seal 120 and the exterior of sleeve 82 to assist in the quick opening of the main valve 16.

The continued downward movement of the piston 58 causes the valve sleeve 82 and its collar 88 to engage the upper surface of the bumper ring 108. In this position, as illustrated in FIGURE 5, the bleed through the piston S8 is still a first-stage or limited bleed of gas through the power piston 58. Further, downward movement resulting from the snap opening of main valve 16 compresses the resilient bumper and will move the piston 58 away from the ring 76 in the vicinity of passage 68, the pin 80 engaging the upper end of the slot 78 on the ring 76. The movement of the piston S8 below the ring 76 provides the second-stage bleeding of greatly increased capacity through the full open passage 68 to allow any trash in groove 74 to be forced through passage 68 and to be conducted to the bore 20 of mandrel 10 as the components begin their rebound resulting from the contact with the bumper ring 108. The second-stage or large-capacity flow through the passage 68 of the piston 58, while only momentary, will provide a suicient ow to blow down any trash, sand or other particles collecting in groove 74 which might interfere with the operation of the pressure-responsive means 14.

The ring 76 will again be seated on the upper surface of the piston 58 to re-establish first-stage bleeding therethrough and will, so long as the pilot. valve 36 remains open, maintain suicient pressure within the pressure chamber 22 to maintain the concentric valving means 16 in its open position.

Considerable impact would normally result from the rebound engagement between the ring 76 and the upper surface of the piston 58. It should be noted from FIG- URE 6, however, that the pin 80 is only a single pin and that when second-stage bleeding occurs, the ring 76 maintains its engagement with the upper surface of the piston 58 on the side of such piston away from the pin 80. This results in the slight cocking or tilting ofthe ring 76 which is illustrated in FIGURE 6. As the piston 58 rebounds, the ring 76 engages the surface of the piston 58 immediately surrounding the passage 68 and the radial groove 74 as it engages the remainder of the upper surface of the piston 58. This tilting action of the ring 76 therefore lessens the impact on rebound vbetween the ring 76 and the piston 58 to prevent damage to the critical area of the piston 58, the radial groove 74, adjacent the passage 68.

When the casing pressure is reduced, the pilot valve 36 closes, and the first-stage bleeding through the piston 58 reduces the pressure within the pressure chamber 22 to the extent that spring 66 moves the assembly upwardly thereby closing the concentric valving means 16. Additionally, an area differential in the main valve 16 will add force tending to close the valve 16 whereby it will close rapidly with a snap action.

As is well-known in the art and taught by the Robinson Patent No. 2,642,812, issued June 23, 1953, the pilot valve may be made responsive to tubing pressure.

With the gas lift valve as described, the sensitivity of the unit to the lift gas pressure is maintained by having a relatively small eiective area in the valve seat of the pilot valve as compared to the cross-sectional area of the bellows which is relatively large. With this construction, the gas lift valve has relatively large-flow capacities without sacricing sensitivity. Further, the valve is economical to manufacture.

The flow capacity of the concentric valving means 16 through the ports 18 and the ports 84 may be made to be as great as or greater than the ilow capacity through the bore 20 of the mandrel. This large-capacity concentric valving means is controlled by the movement of the pressure-responsive means 14 in response to the opening and closing of a side-mounted pilot valve. The concentric main valve means achieves the large-capacity flow with a valve and seat structure which assures sealing of the valving means and avoids the usual high rate of destruction of the seals on prior concentric valves. The -main valve structure also includes a valve seat acting as a check valve to close the main valve even though the main valve member has been actuated. The side-mounted pilot alve is readily installed as an assembly and the structural member of the assembly cooperates with the recess in the mandrel into which a portion of the valve is received to provide a guide for the movement of the pilot valve to assure that it will always return to seating engagement with the pilot valve seat. The particular structure of the piston S8 of the pressure-responsive means 14 is such as to cooperate with the ring 76 to provide the desired first-stage bleed capacity during normal operation of the device and to provide a larger capacity second-stage bleeding at the extreme downward movement of the piston to clear the restricted or iirst-stage bleeding passage of all trash. Further, this largecapacity concentric valve and nonconcentric pilot valve are contained within a tubing mandrel, and the pilot valve is side-mounted thereon so as to be wholly within the general circular contour of the mandrel thereby allowing the gas lift valve of the present invention to be readily lowered into a slim hole producing well on a tubing string. The sensitivity of the gas lift valve is maintained in the device by the use of the pilot valve which controls the large-capacity operation of the main concentric valve.

The foregoing disclosure and description of the invention is illustrative and explanatory thereof, and various changes in the size, shape and materials, as well as in the details of the illustrated construction, may -be made within the scope of the appended claims without departing from the spirit of the invention.

What is claimed is: 1. A gas lift valve, comprising a mandrel having a central bore therethrough and at least one port communicating Vbetween the central bore and the exterior of said mandrel, an annular valve sleeve positioned for longitudinal movement within said mandrel and defining at least one port communicating through said valve sleeve and having a projection surrounding the exterior of said sleeve spaced longitudinally from said port through said sleeve, said mandrel also defining an annular pressure cham-ber and a ow passageway communicating into said chamber, an annular pressure responsive ring lpositioned for reciprocation in said chamber responsive to pressures in said chamber and connected to said annular sleeve member whereby movement of said pressure responsive ring moves said sleeve, and said mandrel defining a bleed passage communicating with said chamber on the opposite side of said pressure responsive ring from said flow passageway,

said pressure responsive ring having a passageway longitudinally therethrough,

an annular ring adapted to be positioned on one face of said pressure responsive ring,

means retaining said annular ring from movement with said pressure responsive ring,

said annular ring restricting the flow through the passageway in said pressure responsive ring in one position of said pressure responsive ring and being positioned away from said passageway in said pressure responsive ring in another position of said pressure responsive ring to allow full flow therethrough whereby trash and sand collecting in said chamber are discharged through said bleed passage, and

an annular valve ring movably positioned Within said mandrel in surrounding relation to said valve sleeve and adapted to engage said projection on said valve sleeve to close communication between the port through said mandrel and the port through said sleeve.

2. A gas lift valve according to claim 1, wherein said pressure responsive ring has opposing pressure surfaces,

one of said pressure surfaces defines an annular recess,

said passageway defined by said pressure responsive .ring communicating 'between said opposing pressure surfaces, and

a radial groove defined in said one of said surfaces and intersecting with said passageway,

said groove being slightly deeper than said recess whereby restricted liow is .provided through said groove to said passageway when said annular ring is seated in said annular recess.

3. A gas lift valve according to claim 1, including a pilot valve mounted on said mandrel,

said ypilot valve controlling iiow through said iiow passageway into said chamber.

4. A gas lift valve according to claim 3, wherein a portion of the exterior of said mandrel includes n surface on which said pilot valve is mounted and a longitudinal recess in said exterior surface of said mandrel,

said pilot valve includes a housing and a valve member,

said housing being secured to said surface with said recess coacting with said housing to guide movement of the valve member of said pilot valve.

5. A gas lift valve according to claim 3, wherein said pilot valve includes a housing secured to said mandrel,

a passage extending radially inward in said housing and communicating from said pilot valve,

a passage extending radially outward in said mandrel and communicating to said annular pressure chamber,

said passages -being connected in radial alignment when said housing is secured to said mandrel to lprovide communication from said pilot valve to said pressure chamber, and

means sealing between said housing and said mandrel around the connection of said passageways.

6. A gas lift valve according to claim 1, including an internal shoulder delined by said mandrel,

a resilient annular bumper positioned within the bore of said mandrel and supported on said shoulder,

said bumper being spaced below the lower end of said valve sleeve in its upper position and adapted to be engaged lby said valve sleeve when it moves to full open position to provide a rebound impetus to the valve sleeve.

7. A gas lift valve according to claim 1, wherein said mandrel detines a transverse slot extending into the space between the mandrel and said sleeve at a position in the lower end of said space whereby trash collecting therein may be discharged through said slot to the exterior of said mandrel.

8. A gas lift valve according to claim 1, including a resilient insert positioned in said projection on the exterior of said sleeve and adapted to be engaged by said annular valve ring to provide a seal closing communication from the exterior of said mandrel 5 to the interior of said sleeve Valve.

9. A gas lift valve according7 to claim 8, wherein said projection is positioned on said sleeve below the port extending through said sleeve so that said insert is positioned out of the flow path of uids flowing 10 through said ports.

References Cited UNITED STATES PATENTS Canalizo 137-155 Garrett 137-155 X Lamb 137-155 Lilly 137-155 Canalizo 137-155 Chenoweth 137-508 ALAN COHAN, Primary Examiner. 

